Endocrine Abstracts

Abstract: A transient thyrotoxicosis followed by a phase of hypothyroidism, sometimes transient and preceding full recovery, is a usual presentation of postpartum thyroiditis, a form of autoimmune thyroiditis occuring after a pregnancy with a worldwide prevalence averaging 5%. Far less commonly, the same presentation may be observed in various circumstances unrelated to pregnancy. We have observed this condition in 6 patients, 4 women, aged 30 to 44 years, and 2 men, 48 and 68 years. They were seen for a thyrotoxicosis, which was clinically mild in 2 cases, and associated in one of them by a painful neck, and more intense in 4 cases. The thyroid was normal or slightly enlarged\. In all of them, the TSH was suppressed, the free T4 elevated and the TSH receptor antibody negative. The diagnosis of autoimmunity was confirmed in 4 of them by high levels of thyroid antibodies, (both anti-TPO and anti-Tg) and in the 2 other cases, was suspected on an echography consistent with this diagnosis. The duration of the thyrotoxic phase was estimated between 4 and 8 weeks, It was followed in 5 of them by a phase of hypothyroidism, which was only transient in 2 cases and persisted in 3 cases. In only 1 case, the thyrotoxicosis was directly followed by full recovery. In one of these patients, the auto-immune thyroiditis was associated with a Systemic Lupus erythematosis, and in a other case it occured in a patienf treated for chronic myeloid leukemia by Nilotinib, a tyrosine kinase inhibitor.

Discussion and conclusion: We have described 6 patients with a transient thyrotoxicosis in the course of a chronic thyroiditis unrelated to pregnancy. This condition is usually described under the terms of ‘silent thyroiditis’ or ‘painless thyroîditis’ (which wouldn’t be appropriate to one of our patients).It may be considered as a rare variant of autoimmune thyroiditis. The occurence of a transient thyrotoxicosis is believed to be due to the release of thyroid hormones, caused by the disruption of thyroid follicles. The factor triggering the transitory destructive process is not known. The thyrotoxic phase must not be confused with Graves’ disease: the most important of the criteria is the absence of thyroid receptor antibody. It must also be differentiated from other causes of transient thyrotoxicosis such as subacute thyroîditis, associated with a painful neck (but pain was also observed in one of our patients), and iodine-induced thyrotoxicosis